Liquid level indicators have previously been disclosed which include indicator lights for indicating the level of a liquid in a container. Turner, in U.S. Pat. No. 1,093,745, discloses a level indicating device which includes a plurality of vertically spaced light bulbs, the light bulbs being energized or deenergized to indicate liquid levels. Huckabee, in U.S. Pat. No. 2,700,153, provides a low water warning signal for the coolant of an engine in order that the engine may be stopped in the event of low coolant level. Smith, in U.S. Pat. No. 3,339,578, discloses an indicator light circuit in which conductors electrically connected to electrodes include resistors and a neon light connected between the conductors, the light being illuminated when the water level falls below the probes. Seil, in U.S. Pat. No. 3,253,820, discloses a water level indicator combined with a portable humidifier operated by a float and switch structure.
The invention relates generally to systems for maintaining a desired level of humidity, such as can be adaptable for use with a piano, it being beneficial to maintain a substantially constant and predetermined humidity level within the interior of a piano. However, the invention finds general application as a liquid level measuring and warning device and can be particularly useful when refill of the system with water cannot be readily observed, the present system indicating that the water level therewithin has been diminished by a predetermined amount and can be replenished by said predetermined amount without fear of overfilling the system even though the portion of the system containing the water is not visible to the user. The invention is further useful in a humidifying system wherein heat is applied by means of an adjustable heating rod to evaporating pads projecting into a reservoir of water. The present humidity control system comprises a water level indicating device provided with a pair of probes which extend into the reservoir of water, the device being electrically controlled by means of a dual humidistat which is plugged into an electrical outlet, there being no waste of current or power in creating humidity in the system. The probes are present in a circuit with a neon indicator light, the circuit being shorted when the water level in the reservoir is sufficiently high to at least cover the lower ends of the probes. Evaporation of the water to a level below the ends of the probes causes the circuit to be completed, thereby activating the neon indicator light. Replenishment of the water supply in the reservoir is thus indicated as being necessary, the amount of water required to so replenish the water supply in the reservoir being a predetermined amount which can thus be added to the reservoir by means of a water conduit extending into the reservoir at the anterior end of said conduit and being located for convenient access at the distal or free end thereof. A predetermined quantity of water can thus be charged into the reservoir through the conduit without overfilling thereof, the reservoir being thereby filled without the need for visual observation thereof. The circuit of the invention further includes a pair of limiting resistors which limit the current within the circuit to 0.5 milliamperes, the maximum allowed in view of safety considerations. The limiting resistors extend the life of the neon indicator lamp to a period of 20 years or more. The neon indicator light is preferably mounted in a tube assembly having a strain relief bushing provided therein so that a wire connecting the indicator light to the circuit cannot accidentally be pulled from the light.
Accordingly, it is an object of the present invention to provide a humidity control system comprising a liquid level measuring, indicating, and refill device, the device comprising a pair of probes and a neon indicator light in a suitable circuit, the probes being disposed within a liquid reservoir, the level of the liquid therein allowing the circuit to either be completed or be shorted out such that the indicator light is lit when the level of liquid in the reservoir is at a predetermined low level.
It is another object of the invention to provide a humidity control system having a water measurement/warning sub-system and a "blind" refill sub-system, the measurement/warning sub-system indicating the diminution of the water supply in the system by a predetermined amount, the "blind" refill sub-system allowing replenishment of the water supply without the need for visual observation of the water-containing portion of the system to prevent overfilling.
If is a further object of the invention to provide a humidity control system which is readily incorporated into a unitary cooperating construction, which is portable, and which is adapted to be plugged into any readily available electrical outlet.
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.